This invention relates generally to a directional control valve for controlling the flow of fluid between a pump, a motor and a reservoir. More particularly, the invention relates to an electro-hydraulic proportional control valve that provides an accurately controlled fluid flow rate in response to an electrical input signal.
Electro-hydraulic pilot valves are used in the fluid power industry for receiving an electrical input signal and for providing a hydraulic signal in response to the electrical signal. One such electro-hydraulic valve is disclosed in U.S. Pat. No. 3,866,620, the entirety of which is incorporated herein by reference.
The hydraulic signal from the electro-hydraulic pilot valve in these prior art devices is directed to control the position of a directional control valve spool. The directional control valve spool is operable between a neutral position, a leftward position, and a rightward position to direct fluid from a pump to one side of a fluid motor and to return fluid from the other side of the fluid motor to a reservoir. When it is desired to change the flow rate capacity of the directional control valve, it is common practice in the industry to substitute different directional control valve spools with various arrangements and sizes of lands and grooves to provide the desired flow rate capacity.